Abstract:In order to improve the agglomeration and deliquescence of fructose owing to its strong hygroscopicity, the effect of adding wheat gluten (WG) on the hygroscopic properties of freeze-dried fructose were investigated using characterization methods, including hygroscopic curves and isotherms, macroscopic morphological analysis, determination of contact angles, and low-field NMR. Subsequently, the differences in the effects of the two main components of WG, gliadin and glutenin, were compared. The results showed that the addition of WG considerably reduced the equilibrium moisture content (EMC) of the freeze-dried fructose samples. Under conditions of 25 ℃ and 75% relative humidity, the EMCs were 36.33%, 16.00% and 14.61% when the respective mass ratios of fructose to WG were 10:0, 3:7, and 2:8. As the proportion of WG increased, the degree of agglomeration of the sample decreased, whilst the contact angle increased from 11.3 ° to 94.8 °. The Peleg model accurately described the water adsorption process of the fructose-protein system. The EMC of the sample with the addition of glutenin was lower, with a smaller amount of agglomeration compared to that of gliadin. Furthermore, the contact angle of glutenin (88.2 °) was greater than that of gliadin (64.6 °). Low-field NMR results showed that glutenin was more effective at reducing the degree of moisture freedom compared to gliadin. These results demonstrate that WG and its main components have a significant inhibitory effect on the hygroscopicity of fructose, and that glutenin is more effective compared to gliadin for the inhibition of moisture absorption.
